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Sanchez Del Rey A, Sánchez Fernández JM, Gutierrez N, Martínez A, Santaolalla Montoya F. Morphological and morphometric study on human Scarpa ganglion development. Acta Otolaryngol 2013; 133:352-60. [PMID: 23350596 DOI: 10.3109/00016489.2012.756147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
CONCLUSION In Scarpa neurons the cell and nuclear area increases and nuclear/cytoplasm ratio decreases with fetal age (p < 0.0001). There are statistically significant differences in cell area between all fetal groups, except for the interval 45-74 mm crown-rump-length (CRL). Displacement of a neuron within the internal auditory meatus (IAM) occurs from 9 weeks in the fetus until the neonate. METHODS A light microscopic histomorphometric study of the Scarpa ganglion in human fetuses from spontaneous abortions measuring 45, 74, 90, 134, 145 and 270 mm CRL and a from a 1-day-old neonate (360 mm) was carried out. Cell and nuclear area, ganglion area and distances from the Scarpa ganglion neurons to the endocranial porus of the IAM were measured. RESULTS In the 45, 74, 90 and 134 mm CRL human fetuses the cartilaginous labyrinthine capsule appears divided by the facial nerve and the Scarpa ganglion into two compartments: rostral and dorsal. Ovoidal Scarpa ganglion in the 45 mm CRL lies within the IAM near its endocranial porus (15 µm). In the otic capsule of the 145 mm CRL fetus an endochondral ossification appears in the IAM base, where Scarpa ganglion neurons are displayed in two groups: superior and inferior divided by a vascular-connective septum. This anatomy remains from this specimen until the neonate specimen.
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Affiliation(s)
- Ana Sanchez Del Rey
- Otorhinolaryngology Department, School of Medicine, University of the Basque Country, UPV/EHU, Bilbao, Vizcaya, Spain.
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Leake PA, Hradek GT, Hetherington AM, Stakhovskaya O. Brain-derived neurotrophic factor promotes cochlear spiral ganglion cell survival and function in deafened, developing cats. J Comp Neurol 2011; 519:1526-45. [PMID: 21452221 PMCID: PMC3079794 DOI: 10.1002/cne.22582] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Postnatal development and survival of spiral ganglion (SG) neurons depend on both neural activity and neurotrophic support. Our previous studies showed that electrical stimulation from a cochlear implant only partially prevents SG degeneration after early deafness. Thus, neurotrophic agents that might be combined with an implant to improve neural survival are of interest. Recent studies reporting that brain-derived neurotrophic factor (BDNF) promotes SG survival after deafness have been conducted in rodents and limited to relatively short durations. Our study examined longer duration BDNF treatment in deafened cats that may better model the slow progression of SG degeneration in human cochleae, and this is the first study of BDNF in the developing auditory system. Kittens were deafened neonatally, implanted at 4-5 weeks with intracochlear electrodes containing a drug-delivery cannula, and BDNF or artificial perilymph was infused for 10 weeks from a miniosmotic pump. In BDNF-treated cochleae, SG cells grew to normal size and were significantly larger than cells on the contralateral side. However, their morphology was not completely normal, and many neurons lacked or had thinned perikaryl myelin. Unbiased stereology was employed to estimate SG cell density, independent of cell size. BDNF was effective in promoting significantly improved survival of SG neurons in these developing animals. BDNF treatment also resulted in higher density and larger size of myelinated radial nerve fibers, sprouting of fibers into the scala tympani, and improvement of electrically evoked auditory brainstem response thresholds. BDNF may have potential therapeutic value in the developing auditory system, but many serious obstacles currently preclude clinical application.
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Affiliation(s)
- Patricia A Leake
- Departmant of Otolaryngology-Head and Neck Surgery, University of California San Francisco, San Francisco, California 94143-0526, USA.
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Rusznák Z, Szucs G. Spiral ganglion neurones: an overview of morphology, firing behaviour, ionic channels and function. Pflugers Arch 2008; 457:1303-25. [PMID: 18777041 DOI: 10.1007/s00424-008-0586-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 08/22/2008] [Accepted: 08/26/2008] [Indexed: 11/29/2022]
Abstract
The spiral ganglion cells provide the afferent innervation of the hair cells of the organ of Corti. Ninety-five percent of these cells (termed type I spiral ganglion neurones) are in synaptic contact with the inner hair cells, whereas about 5% of them are type II cells, which are responsible for the sensory innervation of the outer hair cells. To understand the function of the spiral ganglion neurones, it is important to explore their membrane properties, understand their activity patterns and describe the variety of ionic channels determining their behaviour. In this review, a brief description is given of the various experimental methods that allow the investigation of the spiral ganglion cells, followed by the discussion of their action potential firing patterns and ionic conductances. The presence, distribution and significance of the K(+) currents of the spiral ganglion cells are specifically addressed, along with the introduction of the putative subunit compositions of the relevant voltage-gated K(+) channels.
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Affiliation(s)
- Zoltán Rusznák
- Department of Physiology, Medical and Health Science Centre, University of Debrecen, Debrecen, P O Box 22, H-4012, Hungary.
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Mo ZL, Adamson CL, Davis RL. Dendrotoxin-sensitive K(+) currents contribute to accommodation in murine spiral ganglion neurons. J Physiol 2002; 542:763-78. [PMID: 12154177 PMCID: PMC2290456 DOI: 10.1113/jphysiol.2002.017202] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We have previously identified two broad electrophysiological classes of spiral ganglion neuron that differ in their rate of accommodation (Mo & Davis, 1997a). In order to understand the underlying ionic basis of these characteristic firing patterns, we used alpha-dendrotoxin (alpha-DTX) to eliminate the contribution of a class of voltage-gated K(+) channels and assessed its effects on a variety of electrophysiological properties by using the whole-cell configuration of the patch-clamp technique. Exposure to alpha-DTX caused neurons that initially displayed rapid accommodation to fire continuously during 240 ms depolarizing test pulses within a restricted voltage range. We found a non-monotonic relationship between number of action potentials fired and membrane potential in the presence of alpha-DTX that peaked at voltages between -40 to -10 mV and declined at more depolarized and hyperpolarized test potentials. The alpha-DTX-sensitive current had two components that activated in different voltage ranges. Analysis of recordings made from acutely isolated neurons gave estimated half-maximal activation voltages of -63 and 12 mV for the two components. Because alpha-DTX blocks the Kv1.1, Kv1.2 and Kv1.6 subunits, we examined the action of the Kv1.1-selective blocker dendrotoxin K (DTX-K). We found that this antagonist reproduced the effects of alpha-DTX on neuronal firing, and that the DTX-K-sensitive current also had two separate components. These data suggest that the transformation from a rapidly adapting to a slowly adapting firing pattern was mediated by the low voltage-activated component of DTX-sensitive current with a potential contribution from the high voltage-activated component at more depolarized potentials. In addition, the effects of DTX-K indicate that Kv1.1 subunits are important constituents of the underlying voltage-gated potassium channels.
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Affiliation(s)
- Zun-Li Mo
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854-8082, USA
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Thiers FA, Burgess BJ, Nadol JB. Prevalence and ultrastructural morphology of axosomatic synapses on spiral ganglion cells in humans of different ages. Hear Res 2000; 150:119-31. [PMID: 11077197 DOI: 10.1016/s0378-5955(00)00193-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Axosomatic synapses were found on human spiral ganglion cells (HSGCs). Ultrastructural characterization and calculation of the prevalence of these synapses were performed by electron microscopic semi-serial sections of both type I and type II HSGCs, in specimens from subjects of ages 1 day, 14 days, 21 years and 51 years. Synapses on type I HSGCs were extremely rare. In contrast, axosomatic synapses were present on approximately 50% of type II HSGCs of a young adult. This prevalence seemed to vary by age. Thus, no synapses were found in a 1-day old neonate, few in a 14-day old, and on approximately 15% of the type II SGCs from a 51-year old specimen. The origin of the nerve fibers synapsing on the type II HSGCs could not be determined. In view of the fact that some of the fibers projected from the intraganglionic spiral bundle, which is known to contain olivocochlear efferents, these fibers may represent an efferent pathway to the spiral ganglion. However, since there was morphological evidence of more than one type of nerve fiber synapsing on type II HSGCs, other neural origins must be considered. Although the physiological function of these synapses is unknown, they may mediate pre-synaptic neural modulation of the type II HSGCs at the level of the spiral ganglion.
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Affiliation(s)
- F A Thiers
- Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA
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Sánchez Del Rey A, Sánchez Fernández JM, Martínez Ibarguen A, Santaolalla Montoya F. Morphologic and morphometric study of human spiral ganglion development. Acta Otolaryngol 1995; 115:211-7. [PMID: 7610807 DOI: 10.3109/00016489509139294] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A light microscopic study of the spiral ganglion was done in human embryos and fetuses measuring 45, 50, 60, 74, 90, 134, 270 mm crown-rump length (crl), and in a one-day-old neonate. Morphometric evaluations of i) cell and nuclear area, ii) nuclear area/cell area ratio, iii) ganglion area, iv) cell concentration/surface unit, and v) distance between the first neuron and the receptor were made, and the results statistically evaluated. In earlier stages of development, spiral ganglion primordia appeared as a cluster of neuroblasts and some schwannoblasts immersed in the mesenchymal tissue, close to the ductus cochlearis. A honeycomb pattern in the spiral ganglion neurons was observed in the basal turn of a 74 mm crl fetus. In later stages, the basal turn of a 90 mm crl fetus showed a spatial organization. Peripheral and central fibers of the acoustic nerve appeared stratified in early periods of development (45 mm crl embryo). From this stage on, both phenomena progress apicalwards until the neonatal period. A significant decrease in the nuclear area/cell area ratio was observed from the 134 mm crl fetus (17 weeks) to the neonatal stage in all turns. This led to a significant increase in cellular area from the 270 mm crl fetus (32 weeks) to the neonate, with no significant variation in nuclear area. The distance from the primordium of the organ of Corti to the spiral ganglion in the interval between 45 and 74 mm crl showed a significant increase in all turns.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A Sánchez Del Rey
- Otolaryngology Department, Basurto Hospital, School of Medicine, University of the Basque Country, Bilbao, Spain
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Xu SA, Shepherd RK, Chen Y, Clark GM. Profound hearing loss in the cat following the single co-administration of kanamycin and ethacrynic acid. Hear Res 1993; 70:205-15. [PMID: 8294265 DOI: 10.1016/0378-5955(93)90159-x] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Co-administration of kanamycin (KA) with the loop diuretic ethacrynic acid (EA) has previously been shown to produce a rapid and profound hearing loss in guinea pigs. In the present study we describe a modified technique for developing a profound hearing loss in cats. By monitoring the animal's hearing status during the intravenous infusion of EA the technique minimizes the effects of individual variability to the drug regime. Seven cats received a subcutaneous injection of KA (300 mg/kg) followed by intravenous infusion of EA (1 mg/min). Click-evoked auditory brainstem responses (ABRs) were recorded to monitor the animal's hearing during the infusion. When the ABR thresholds rose rapidly to levels in excess of 90 dB SPL the infusion of EA was stopped. This occurred at EA doses of 10-25 mg/kg, indicating considerable individual variability to the deafening procedure. However, there was a strong negative correlation (r = -0.93) between the EA dose and body weight which accounted for much of this variability. Subsequent ABR monitoring showed that this profound hearing loss was both bilateral and permanent. Significantly, blood urea and creatinine levels, monitored for periods of up to three days after the procedure, remained within the normal range. Furthermore, there was no clinical evidence of renal dysfunction as indicated by weight loss or oliguria. Cochlear histopathology, examined after a two months to three year survival period, showed an absence of all inner and outer hair cells in the majority of cochleas. The extent of loss of spiral ganglion cells was dependent on their distance from the round window and the period of survival following the deafening procedure. Clearly, the degeneration of spiral ganglion cells continued for several years following the initial insult. Finally, we observed no evidence of renal histopathology. In conclusion, the co-administration of KA and EA produces a profound hearing loss in cats without evidence of renal impairment. Monitoring the animal's hearing status during the procedure ensures that the dose of EA can be optimised for individual animals. Moreover, it may be possible to adapt this procedure to produce animal models with controlled high frequency hearing losses.
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Affiliation(s)
- S A Xu
- Department of Otolaryngology, University of Melbourne, Parkville, Victoria, Australia
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Chiong CM, Burgess BJ, Nadol JB. Postnatal maturation of human spiral ganglion cells: light and electron microscopic observations. Hear Res 1993; 67:211-9. [PMID: 8340274 DOI: 10.1016/0378-5955(93)90249-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The presence of two types of ganglion cells, based on cell size and other morphologic parameters, is well established in the adult mammalian and human spiral ganglion. On the other hand, there is little data concerning cell morphology in the neonatal spiral ganglion. The present study was undertaken to evaluate the differences in the morphometry and distribution of cell types in the spiral ganglion of the human neonate as compared to the adult. A total of five human temporal bones from two neonates and three infants were included in this study. Light microscopic analysis of all specimens was performed, and electron microscopic evaluation of a 14 day old neonatal spiral ganglion was accomplished. The segmental density of spiral ganglion cells was higher in the neonate than in the adult. The prevalence of type II spiral ganglion cells was higher in the neonate than has been reported in the adult, particularly in the middle and apical turns where type II cells constituted 24% and 26% of all ganglion cells, respectively. The prevalence of type II ganglion cells decreased with age, particularly in the middle and apical turns. In the neonate, the maximal cross sectional area of type I neurons increased from the base to the apex and seemed to increase with age especially in the basal turn. The present study strongly supports a clear differentiation of type I and type II ganglion cells in the human neonate and that the prevalence of type II cells is greater in the neonate than the adult. This finding is discussed with reference to postnatal development of the spiral ganglion.
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Affiliation(s)
- C M Chiong
- Department of Otolaryngology, Sunnybrook Health Science Center, Toronto, Ontario, Canada
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